The Biosynthesis and Measurement of Immunoglobulin E in the Rat

In Section 1, various methods employed for the quantification of IgE are discussed, and detailed accounts are given of the techniques used in this laboratory. Total IgE levels in human sera have been estimated using the Phadebas radioimmunosorbent test (RIST). This is a competitive radioimmunoassay in which IgE in a sample competes with radiolabelled IgE for sites on sephadex-anti-IgE particles. The usefulness and limitations of the test are discussed. A rat radioimmunosorbent test (RIST), and the Rowe modification of the Mancini single radial diffusion test are both described in detail. Both tests measure total IgE levels in rat sera. The rat RIST is a direct 'sandwich' radioimmunoassay in which IgE in a sample binds to anti rat IgE bound to activated paper discs. Finally addition of radiolabelled anti-rat IgE acts as a marker for the amount of sample IgE bound, RIST is more sensitive than the Rowe-Mancini test, detecting IgE levels as low as 10ng/ml. Technical aspects of the tests are discussed in detail. Antigen specific rat IgE is measured by the radio allergo-sorbent (RAST) and passive cutaneous anaphylaxis (PCA) tests. The RAST is based on the same principle as the rat RIST, but antigen instead of anti-IgE is bound to activated paper discs. The RAST has been used in this laboratory to detect IgE directed against egg albumin and N. brasiliensis antigens, and of the two systems the egg albumin RAST is the more efficient, N. brasiliensis / RASTS Radio allergosorbent tests being hampered by lack of pure antigen preparations. The RAST was found to be only partially reproducible, but extremely sensitive. The PCA test is the test of choice in this laboratory for the quantification of antigen specific IgE, and is discussed in detail in this section. Section III presents a study of the relationship in time between the elevation of total serum IgE, the parasite-specific IgE response, and the potentiated IgE response to unrelated antigen which occurs in rats following infection with the worm parasite N. brasiliensis. During a first infection the potentiated IgE response (to egg albumin) and elevation of total IgE occur synchronously rising to a peak on days 12-14 after infection, with the fastest rate of increase occurring between days 8 and 10. N. brasiliensis-specific IgE rises to a peak some 2-3 weeks later when both total IgE and the potentiated response have largely declined. A strain difference is shown in that Wistar rats produce far lower levels of total and parasite-specific IgE than Hooded Listers. Events following reinfection differ in that total IgE rises more rapidly, very high levels being reached 6 days after reinfection together with a secondary specific IgE response to N. brasiliensis. The total IgE level, however, rises by a far greater factor than parasite-specific IgE and declines rapidly while the parasite-specific response declines slowly over many weeks. The egg albumin response is not repotentiated. It is proposed that the total IgE response and the potentiated IgE response which forms a small component of it results from the release of a non-specific IgE-stimulating factor produced by N. brasiliensis-specific T cells. In this scheme the same or similar cells are involved in the production of N. brasiliensis-specific IgE through a separate specific helper function. In Section II experiments were described in which primary and booster IgE antibody responses were elicited in Hooded Lister rats by the intradermal injection or oral administration of very small quantities of egg albumin. Oral immunization was effected by giving antigen by stomach tube or in the drinking water. The minimum primary dose of antigen found to be effective was I ug intradermally and 10 mug orally, administered together with an intraperitoneal injection of B. pertussis adjuvant. In rats immunized with these doses secondary responses could be evoked by giving even smaller quantities of antigen, thus 1 ng intradermally or 1 mug orally without adjuvant. Smaller challenge doses were not tried. Large primary doses of antigen (>100 mug) presented by these routes were, on the other hand, found to be inhibitory to the production of secondary IgE responses, this effect being similar to that observed in previously reported intraperitoneal immunization experiments. By contrast with previous experiments, however, tertiary responses could be obtained following immunization by these routes, and I believe this to be a reflection of the absorption of smaller and therefore less inhibitory quantities of antigen. The results are discussed in relation to the control of IgE antibody production, current concepts of the control of antigen absorption through mucosal barriers, and possible implications for the genesis of naturally occurring IgE responses in man

Heterogeneous nucleation at hydrophobic interfaces

Crystal nucleation is a ubiquitous process that plays an important role in a range of environmental, biological and industrial processes. It is well accepted that nucleation most commonly occurs heterogeneously at interfaces, and a number of mechanisms have previously been explored that contribute to this effect. Nucleation experiments are often conducted in small scale experimental setups, where the interfaces present are significantly different to those present in normal, macroscale crystallisations. Despite the prevalence of heterogeneous nucleation, the effects of these very particular interfaces are often neglected when analysing the data from such experiments. This thesis will demonstrate the impacts that these interfaces can have on nucleation using a model system of aqueous glycine solution, and will demonstrate a novel concentration effect that facilitates heterogeneous nucleation and is distinct from previously investigated heterogeneous nucleation mechanisms. Results of experiments will be reported for glycine solutions with and without contact with a tridecane oil interface. These results demonstrate that the presence of the oil significantly increases the nucleation rate of glycine. This is a surprising result as the nonpolar hydrophobic tridecane interface would not be expected to enhance the nucleation of the highly polar, hydrophilic glycine. Classical molecular dynamics simulations reveal significantly enhanced vs depleted glycine concentrations at the oil–solution vs air–solution interfaces, respectively. It is proposed that this interfacial concentration effect facilitates heterogeneous nucleation, and that it is due to dispersion interactions between the interface and the solution molecules. To confirm this, model interfaces with tuneable interface–solution interactions were implemented to the molecular dynamics simulations. The solution composition at the interface was found to be strongly dependent on the strength of the dispersion interactions between the interface and the solution. In contrast, while the electrostatic interactions between the interface and the solution were also found to influence the interfacial solution composition, the observed effects are significantly weaker than those observed for the dispersion interactions. These effects have been observed for glycine solutions at a tridecane interface, however it is expected that the same mechanism will be present in a wide range of solution–interface systems. Deeper understanding of these efffects will allow for control over the interfacial concentration in order to design effective nucleants for the enhancement of nucleation, or to suppress nucleation for anti-fouling purposes.Crystal nucleation is a ubiquitous process that plays an important role in a range of environmental, biological and industrial processes. It is well accepted that nucleation most commonly occurs heterogeneously at interfaces, and a number of mechanisms have previously been explored that contribute to this effect. Nucleation experiments are often conducted in small scale experimental setups, where the interfaces present are significantly different to those present in normal, macroscale crystallisations. Despite the prevalence of heterogeneous nucleation, the effects of these very particular interfaces are often neglected when analysing the data from such experiments. This thesis will demonstrate the impacts that these interfaces can have on nucleation using a model system of aqueous glycine solution, and will demonstrate a novel concentration effect that facilitates heterogeneous nucleation and is distinct from previously investigated heterogeneous nucleation mechanisms. Results of experiments will be reported for glycine solutions with and without contact with a tridecane oil interface. These results demonstrate that the presence of the oil significantly increases the nucleation rate of glycine. This is a surprising result as the nonpolar hydrophobic tridecane interface would not be expected to enhance the nucleation of the highly polar, hydrophilic glycine. Classical molecular dynamics simulations reveal significantly enhanced vs depleted glycine concentrations at the oil–solution vs air–solution interfaces, respectively. It is proposed that this interfacial concentration effect facilitates heterogeneous nucleation, and that it is due to dispersion interactions between the interface and the solution molecules. To confirm this, model interfaces with tuneable interface–solution interactions were implemented to the molecular dynamics simulations. The solution composition at the interface was found to be strongly dependent on the strength of the dispersion interactions between the interface and the solution. In contrast, while the electrostatic interactions between the interface and the solution were also found to influence the interfacial solution composition, the observed effects are significantly weaker than those observed for the dispersion interactions. These effects have been observed for glycine solutions at a tridecane interface, however it is expected that the same mechanism will be present in a wide range of solution–interface systems. Deeper understanding of these efffects will allow for control over the interfacial concentration in order to design effective nucleants for the enhancement of nucleation, or to suppress nucleation for anti-fouling purposes

Implementing immersive virtual reality in higher education:a qualitative study of instructor attitudes and perspectives

The current study aimed to understand the attitudes and perceptions of higher education (HE) instructors who have previously used immersive virtual reality (IVR) in teaching. This study employed a qualitative design by conducting semistructured interviews with HE instructors from several disciplines and institutions. Using thematic analysis, five major themes were formulated. These included: (a) applications and benefits; (b) curriculum integration; (c) classroom logistics; (d) barriers to application; and (e) evaluation. Instructors were generally positive about using I-VR as a pedagogical tool, proposing a range of novel applications and uses. However, logistical and technical problems were prominent which made implementation and widescale adoption challenging. The implications of these prominent attitudes are discussed, alongside a range of practical recommendations for applied future practic

Avian Behavioral and Physiological Responses to Challenging Thermal Environments and Extreme Weather Events

Birds occupy habitats ranging from Antarctic ice shelves and Arctic tundra to low-latitude deserts and lowland rainforests, and so are exposed to the full range of climates present on Earth. Cold, hot, or variable (on a variety of temporal scales) thermal conditions can present significant thermoregulatory challenges to birds, which typically must maintain body temperatures within narrow physiological tolerance limits. Such challenges may occur in all stages of the annual cycle and in all life stages of birds, so the ability to adjust to these conditions is required to maintain stable populations through time. For this Research Topic, we broadly define a challenging thermal environment as one necessitating behavioral or physiological adjustments to maintain body temperatures at levels appropriate for continued physiological function.Avian abilities to respond to extreme cold and heat are defined by thermoregulatory capacities for heat production or dissipation, respectively. Behavioral responses to temperature challenges can reduce the necessity for and magnitude of physiological adjustments, so together, physiological capacities and behavioral responses determine the probability of survival in thermally challenging situations. Moreover, thermal conditions experienced during reproduction can affect parental investment in the nesting effort and, independently, alter the course of nestling development, with potentially long-term consequences. Behavioral responses to these conditions as well as physiological responses at multiple levels of organization, from organisms to molecules, allow birds to tolerate thermal challenges. Our knowledge of the mechanisms by which birds respond, the time course for such responses, and the impacts on fitness, however, remain incompletely understood. Studies examining behavioral and physiological responses of birds to extreme and/or seasonally variable climates have been a research focus for decades, but recent advances in methods of measurement and analyses of physiological and behavioral traits have led to novel findings regarding the patterns and mechanisms by which birds adjust to challenging thermal environments.This Research Topic examines how thermal conditions in the environment pose challenges to birds and the physiological and behavioral adjustments that birds employ to meet them. Articles for this Research Topic may be original research papers, reviews, or perspectives. Specific themes that we believe are suitable for this Research Topic include, but are not limited to:• Integrative mechanisms underlying bird thermoregulatory capacities contributing to a tolerance of challenging thermal environments and their links to fitness• Influence of thermal conditions during reproduction on parental investment or nestling development• Behavioral responses to challenging thermal conditions and their mechanistic underpinnings• Time courses for physiological adjustments to environmental temperature variation• Physiological and behavioral flexibility associated with daily or seasonal temperature variation• Physiological and behavioral responses and tolerance limits during extreme weather events• Body temperature regulation under challenging thermal conditions and energy or water restrictions, including real-time field measurements and thermal imaging• Body temperature regulation and environmental or ecological drivers of hypometabolic strategies• Physiological consequences of exceeding thermoregulatory capacitie

Interfacial concentration effect facilitates heterogeneous nucleation from solution

Crystal nucleation from solution plays an important role in environmental, biological, and industrial processes and mainly occurs at interfaces, although the mechanisms are not well understood. We performed nucleation experiments on glycine aqueous solutions and found that an oil−solution interface dramatically accelerates glycine nucleation compared to an air−solution interface. This is surprising given that nonpolar, hydrophobic oil (tridecane) would not be expected to favor heterogeneous nucleation of highly polar, hydrophilic glycine. Molecular dynamics simulations found significantly enhanced vs depleted glycine concentrations at the oil−solution vs air−solution interfaces, respectively. We propose that this interfacial concentration effect facilitates heterogeneous nucleation, and that it is due to dispersion interactions. This interface effect is distinct from previously described mechanisms, including surface functionalization, templating, and confinement and is expected to be present in a wide range of solution systems. This work provides new insight that is essential for understanding and controlling heterogeneous nucleation

Understanding the effect of diffusive mixing in antisolvent crystallisation

Antisolvent crystallisation is a process widely applied within the pharmaceutical industry. It relies on the difference in solubility of a solute in two miscible liquids—the solvent and the antisolvent—to create the supersaturation required for crystallisation to occur [1]. The mixing process has a significant impact on the characteristics of the final product [2], since properties such as the crystal size distribution and the final crystal polymorph obtained are influenced by local supersaturation values. However, mass transfer in antisolvent crystallisation is not well understood, leading to the occurrence of unexpected and undesired phenomena such as oiling out (i.e. liquid/liquid phase split) or the formation of unwanted crystal phases. Traditionally, the mixing of solute, solvent and antisolvent at the microscale has been described through Fick’s law of diffusion. However, this model considers the driving force for mass transfer to be the gradient in concentration of the components, instead of the more physically accurate gradient in chemical potential. Therefore, it fails to explain non-idealities observed for certain systems including uphill diffusion [3], which is the diffusion of a component against its concentration gradient. The path of the system through the solubility phase diagram is dictated by mass transfer, and unwanted phenomena may occur when non-idealities lead the system to unexpected regions in this phase diagram. The development of a model that accurately predicts and describes these events is essential for their understanding and prevention. In this work, we compare the performance of Fick’s law against the Maxwell-Stefan equations in a system formed by water, ethanol, and glycine, in which the appearance of these phenomena has been reported. Since the Maxwell-Stefan framework considers the chemical potential as the driving force for diffusion, a better description of the mixing process is expected, including the prediction of nonidealities, as this model is more robust from a thermodynamical perspective. The simulation results are compared to experimental diffusion measurements obtained through Raman spectroscopy, with the expectation that the Maxwell-Stefan equations will adjust better to the experimental results. This framework has the potential to greatly enhance our understanding of diffusive mixing processes not only in antisolvent crystallisation, but also in any other chemical process in which diffusion of nonideal solutions takes place. Ultimately, this will lead to safer, more robust manufacturing of chemical and pharmaceutical products

Glass transition temperature of a polymer thin film : statistical and fitting uncertainties

The polymer glass transition is an important property in a wide variety of applications. The glass transition temperature of a polymer composite or confined thin film can be significantly different to the pure polymer. Molecular dynamics simulations are useful for providing molecular level insight and prediction, particularly at interfaces, that are not easily observable experimentally. However, there are significant methodological uncertainties in calculating the polymer glass transition temperature using molecular dynamics simulations. In this work we investigate how the cooling method, fitting range and statistical variation affects the calculated glass transition temperature of polyethylene. We found that it is necessary to perform multiple independent simulations to obtain statistically significant results, and that appropriate fitting ranges must be chosen. The methodological findings were used to investigate the difference in glass transition temperature between pure polyethylene and a polyethylene film confined between graphene surfaces. It was found that the glass transition temperature of a 9 nm thick confined film was higher than bulk polyethylene by approximately 15 K

Editorial: Avian behavioral and physiological responses to challenging thermal environments and extreme weather events

No abstract available.This work was supported by the U.S. National Science Foundation (IOS 1021218 to DS) and the National Research Foundation of South Africa (Grant 119754 to AM). FV was supported by a Discovery grant from the Natural Sciences and Engineering Research Council of Canada (Number 2020-05628). AN was supported by the Swedish Research Council (Grant 2020-04686).http://frontiersin.org/Ecology_and_Evolutiondm2022Zoology and Entomolog

Unravelling anomalous mass transport in antisolvent crystallisation

Antisolvent crystallisation is a process widely applied within the pharmaceutical industry. It relies on the difference in solubility of a solute in two miscible liquids—the solvent and the antisolvent—to create the supersaturation required for crystallisation to occur [1]. Since local supersaturation values affect the properties of the final product [2], mixing plays a major role in this process. However, mass transfer in this context is not well understood, leading to the formation of unwanted crystal phases or to undesired phenomena such as oiling out (i.e. separation of the solute via the formation of a second liquid phase). Traditionally, mixing in the microscale has been described through Fick’s second law. However, this model considers composition gradients as the driving force for mass transfer, instead of the more physically accurate gradient in chemical potential. Thus, it fails to explain non-idealities such as uphill diffusion [3], which is the diffusion of a species against its concentration gradient. Additionally, this model assumes ideal behaviour, but unwanted phenomena, such as oiling out, can occur when non-idealities lead to unexpected regions of the phase diagram. Thus, developing a model that accurately predicts and describes micromixing is essential for understanding and preventing these undesired events. In this work, we propose the modeling of an antisolvent crystallisation system through the Cahn-Hilliard phase-field model [4], coupled with either the Fickian or the Maxwell-Stefan diffusion coefficient. The system, in which the appearance of undesired phenomena has been reported, is formed by water, ethanol, and glycine. Since the Cahn-Hilliard model considers the driving force for mass transfer to be the minimization of the free energy, a better description of the mixing process is expected than through Fickian diffusion. Regarding its comparison with the Maxwell-Stefan model [3], a similar outcome is expected except when close to the spinodal region, in which the Cahn-Hilliard model will prove to be superior. Since this model considers the interphase free energy, it is suitable for the description of phase changes such as spinodal decomposition. Thus, it is also potentially capable of simulating oiling-out. The simulation results will be compared to experimental diffusion measurements obtained through Raman spectroscopy, with the expectation that the Cahn-Hilliard model will adjust better to the experimental results. This framework can greatly enhance our understanding of diffusive mixing processes and liquid-liquid separation phenomena in any chemical process in which diffusion of non-ideal solutions takes place. Ultimately, this will lead to safer, more robust manufacturing of chemical and pharmaceutical products